Telephone-receiver.



No. 863,253. PAT-BNTED AUG. 13; 1907. 5' W. BANKHEAD- TELElj ONE RECEIVER. APELIOATIEN HLED Nov. 17. 190s.

NVNTo/e A TTU/ENE V5- WILLIAMv ROBERT BANKEEAD, or BEEMEEfroN. WASHINGTON.

' TELEPHONE-RECEIVER.

To allnvhoir 'it 'may concern: K

Be it known that I,'W1LL1AM' ROBERT BANKHEAD,

a citizenoi the United States, residing at Bremerton,

'bipolar receiver in which the diaphragm forms a part oi the magnetic circuit. l

A still further object oi the invention is to provide a novel constructionof magnet in which one of the pole pieces is so shaped as to form a seat for the diaphragm and servos further as a means for supporting all oi the metallic parts of the receiver within an insulating Oshell. 1

With these and other objects in ViewL as willmore fully hereinafter appear, the invention consists in certain novel features oi construction and arrangement of parts, hereinafter fully described, illustrated in the accompanying drawings, and particularly, pointed out in the appended claims,'it being understood that lvarious changes in the form, proportions, size and yminor details oi the structure may be made without' departing from the spirit or sacrificing any of the advantages oi the invention. n

In the accompanying drawings-Figure 1 is a sectional elevation oi a telephone receiver constructed in accordance with the invention. Fig. 2 is a detail perspective Viewl oi the metallic parts O the receiver removed from the shell. Fig. 3 is a transverse sectional View on the line 3 3' oi Fig. 1f l Similar numerals of reference are employed to indicate corresponding parts throughout the several g ures of the drawings. y v

The shell 1U and cap 11 have a threaded connection and are of any desired shape and size, the shell and cap being formed ol hard rubber or similar material as usual. ,Arranged within Athe shell is a permanent i horseshoe-'magnet 15 havingtn-o separate polel piece l() and 1.7, the pole piece 1G being flattened at one end where it is connected to one cnd of the horseshoe magnet, and its opposite end being circular in cross section and formiugthe core of the usual coil which is connected in any ordinary manner in the telephone or other lcircuit. This pole piece 16 is slightly oliset, so as to bring its extreme end directly opposite the centcr o the diaphragm 18. I.

Thep'ole piece 17 is shaped to form an approximately irustb conical shell, but this shell is cut away on one Specification of Lettersflatent.

Application filed November 17, 1906. Serial No. 843,925.

Patented Aug.` 13, 190'?.

side, that is, the side toward the'leg of the magnet carrying the pole piece 16 as shown, so as t0 tend to localize the magnetic lines of f orce, and this shell is provided -with an annular fiange 20 that forms a seat for the .djaplu-agm'lS, and together with the diaphragm is confined between the ear cap and the end of the main shell 10. The tapering or conical portion of this 'pole picco conespond sapproximately in contour to the outer end oi the shell 10, and when forced therento by screwing on the cap, will form asupport/ior the whole of the metallic parts oi the receiver, so that auxiliary Iastenings are rendered unneccssaryfmnd the magnet' may be readily removed from the shell when sary ,by merely unscrewing the cap 1l.

By making the pole piece 17 o irusto-conical shape not only is it made to conormto the shape of the shell 10 but it also forms a very rigid and stiff support for the magnet, and since this pole piece 17 constitutes the only support lor the magnet 'within the casing, it serves to maintain the diaphragm and the contiguous end of the IlGCeS- pole piece 16 in practically constant relation one to the other, so that wheir once adjusted the free end of the pole piece 16 Will always have the same position relative to the diaphragm thatit had when initially `ad justed. This is due' to making the pole piece 17, 'be' tween the flange or ring 20 and its point 0i' Connection with the corresponding leg of the magnet, oi'such shape as to constitute a stiff or rigid connection. The'annular'u'ng or'iange 20, it will ,b e observed, isfmade integral with the {ruste-conical portion of the pole'p'iece 17, thus reducing .the number of parts andsimplifying the manufacture, s ince thispole piece'and flange 0r,- ring may he made in one stamping. It'will also be ob-v) v served that the h'usto-conical portion'extends entirelyv around the casing and terminates in a lip by-which it is connected to thc corresponding leg of the magnet. v

. v The pole piece lYhasv a attened end for engagementl with the cnd of the horseshoe magnet, and itfwill he noted that both pole pieces arearranged at the inuerad.-

jacent faces ol' the ends of the horseshoe magnet, and lhcsc are held in spaced relation by a block 22 formed o zinc or other diamagnetic material while the parts are held assembled by one or more rivets 23 formed of brass, copper, or olherdianlagnetic material. l

I As. the diaphragm in, contact with the pole piece 17 Y ywhich constitutes onooi the poles of the magnet and located 'vr-1y closeto the end of the opposite pole piece, thexnagnctic circuit is nearly complete, there being but a very small gap between the two pole pieces and the receiver being thus rendered extremely sensitive. -As the two polesof the magnetare thus brought. l

directlyopposite eachother at the exact center of the diaphragm where the magnet-ic'pullmost effective', the diaphragm becomes more delicately responsive to voice currentsythan `where thefordinary'hi' olarreceiverisemployed.

Cil

` coil on said pole piece, a polar extension of the'otherleg 0f the magnet made of magnetic material and of frustoconical shape and cut away on the side adjacent to the other leg of the magnet to localize the magnetic lines of force, an outwardly extendingA ring or flange formed integral with the buse of the said cone-shaped polar extension, a diaphragm in magnetic-contact with and supported by ther-ing or flange, a casing inclosing the magnet and polar extension' thereof, Iand a cap for clamping the diaphragm and the flange of the polar extension to the casing.

2. A magneto-electric telephone receiver comprising a permanent horse-shoe magnet with legs of equal length, a pole piece of magnetic material in contact with the inner face of one leg of the magnet, a receiver coil on said pole piece, another pole piece of magnetic material of frustriconicnl shape having an extension at its smaller end in contact with the inner face of the other leg of the magnet and its outer end formed into an outwardly extending ring or flange integral with the body of the'polar extension, a diaphragm in magnetic contact with said ring or flange, a spacing block of dlamagnetic material between the contiguous faces of the polar extensions adjacent to the free ends of the legs of the magnet and held thereto by suitable securing means, a casing for the magnetic parts of the telephone receiver, and a cap for the cnsing clamping the diaphragm and frusta-conical polar extension to the casing.

In testimony that I claim the foregoing as my own, l have hereto axed my signature in the presence of two lwitnesses. t.

WILLIAM ROBERT BANKHEAD.

Witnesses W. A. Hom,

PAUL MELMER.. 

